Lycopersicon pimpinellifolium as a source of resistance to the plant pathogen phytophthora infestans

ABSTRACT

The present invention involves tomato plants (Lycopersicon esculentum) that are resistant to the tomato strain of P. infestans races 0 and 1. Lycopersicon pimpinellifolium plants which are resistant to the tomato strain of P. infestans races 0 and 1 are used to construct the tomato plants of the present invention. The preferred Lycopersicon pimpinellifolium used in the present invention is designated as LA 2533.

BACKGROUND OF THE INVENTION

For more than a century, late blight on tomato and potato plants hasbeen a cause of concern to plant breeders. Late blight is common inareas that have cool wet weather and it can be devastating during therainy season when the humidity is high. Although late blight is aworldwide problem, it is particularly prevalent in the eastern UnitedStates, Mexico and the Far East.

Late blight is caused by a fungus called Phytophthora infestans ("P.infestans"). Phytophthora infestans can survive on plant debris, potatotubers, and also on Solanaceous weeds. Spores of this fungus aretypically disseminated during windy, rainy periods; however, the funguscan be disseminated on infected plant debris and fruit. Upon landing onthe leaves, stems and fruit of tomato plants, spores can rapidly infectthe plant tissues causing tissue collapse and eventual death of theplant.

Presently, there have been two physiologic races described for P.infestans in tomato. The first is P. infestans race 0 which ispathogenic on commercial varieties that contain no resistance genes. Thesecond is P. infestans race 1 which is pathogenic on commercialvarieties that contain the Ph₁, resistance gene.

In 1952, resistance to P. infestans was reported in a wild tomatorelative, Lycopersicon pimpinellifolium. This resistance was found to beconferred by a single dominant gene (Ph₁ ; formerly known as TR₁) thatgave resistance to the tomato strain of P. infestans race 0. However,the tomato strain of P. infestans race 1 overcomes the resistanceconferred by Ph₁. See Gallegly, M. E,. "Resistance to the Late BlightFungus in Tomato," (1960) Campbell Plant Science Seminar p. 116. Inaddition, multigenic resistance was identified in the tomato line WestVirginia 700 (PI204996). This resistance was not complete and conferredonly a tolerance to P. infestans race 0 and 1. When the environmentalconditions were favorable for P. infestans race 1 development, thesetolerant plants sustained significant disease.

The cultivated tomato, Lycopersicon esculentum, is one of the mostimportant vegetable crops in the United States and worldwide, withseveral million tons being produced each year in the United Statesalone. The commercial importance of the crop has necessitated a constanteffort to improve cultivated varieties. Therefore, there is a need forcultivated tomato varieties that exhibit disease resistance to P.infestans race 1.

It is an object of the present invention to disclose a novelLycopersicon pimpinellifolium cultivar that can be used as a source ofresistance to the tomato strain of P. infestans race 1. It is a furtherobject of this invention to provide Lycopersicon esculentum plants whichare resistant to the tomato strain of P. infestans, races 0 and 1 andremain resistant to P. infestans race 1 in the field when the diseasepressure is high.

SUMMARY OF THE INVENTION

The present invention involves a method for producing tomato plants(Lycopersicon esculentum) which are resistant to the tomato strain of P.infestans races 0 and 1. These plants are produced by crossing aLycopersicon pimpinellifolium plant which was discovered to contain anew allele(s) which confers resistance to P. infestans races 0 and 1with a Lycopersicon esculentum. After the cross is made, the seed iscollected and regenerated into plants. The resulting plants areevaluated for resistance to the tomato strain of P. infestans races 0and 1. Plants that demonstrate resistance are identified and selected.These selected resistant plants are backcrossed with other Lycopersiconesculentum lines displaying desirable phenotypes to obtain commerciallyacceptable varieties which are resistant to the tomato strain of P.infestans races 0 and 1. This method can also be used to produce seedsthat result in tomato plants (Lycopersicon esculentum) that areresistant to the tomato strain of P. infestans races 0 and 1.

The Lycopersicon pimpinellifolium selection which was discovered to havenovel resistance to P. infestans races 0 and 1 and subsequently used incrosses with L. esculentum is designated as LA 2533, which has also beenreferred to by the inventors as Hope 84.

The plants of the present invention can also be produced by protoplastfusion. To produce plants by protoplast fusion, a protoplast from aLycopersicon pimpinellifolium plant which is resistant to the tomatostrain of P. infestans races 0 and 1 is obtained along with a protoplastfrom a Lycopersicon esculentum. The protoplasts are then fused usingstandard protoplast fusion procedures which are well known in the art.The resulting allogenic cells are obtained and regenerated into plantswhich are evaluated for resistance to the tomato strain of P. infestansraces 0 and 1. Resistant plants are identified and selected.

The Lycopersicon esculentum plants produced according to the method ofthis invention are resistant to the tomato strain of P. infestans, races0 and 1 and remain resistant to P. infestans race 1 in the field whenthe disease pressure is high.

The present invention also involves tomato plants which contain anallele(s) which confers resistance to the tomato strain of P. infestansraces 0 and 1 and seed produced by said tomato plants.

DETAILED DESCRIPTION OF THE INVENTION

The present invention involves the creation of tomato plants(Lycopersicon esculentum) which are resistant to the tomato strains ofP. infestans. Plants are said to be disease resistant if, when exposedto the tomato strains of P. infestans, the plants either fail to exhibitdisease symptoms or exhibit substantially reduced symptoms compared tosusceptible plants. The plants of the present invention are new andnovel because they are resistant to the tomato strain of P. infestans,races 0 and 1.

The inventors of the present invention have discovered Lycopersiconpimpinellifolium plants which contain an allele(s) that confersresistance to the tomato strain of P. infestans races 0 and 1. TheseLycopersicon pimpinellifolium plants can be used to create tomato plants(Lycopersicon esculentum) that are resistant to the tomato strain of P.infestans races 0 and 1. For example, Lycopersicon pimpinellifoliumplants designated as LA 2533 were used to create the plants of thepresent invention. Lycopersicon pimpinellifolium plants designated as LA2533 have also been referred to as Hope 84 by the inventors. Seeds of LA2533 (Hope 84) were deposited with the American Type Culture Collection,12301 Parklawn Drive, Md. 20852, under the provisions of the BudapestTreaty. The seeds were deposited on Dec. 14, 1995 and received ATCCAccession Number 97382. In addition, LA 2533 (Hope 84) is also availablefrom the Rick Center at the University of California-Davis, Davis,Calif. upon request.

The inventors have discovered that LA 2533 plants exhibit resistance tothe tomato strain of P. infestans, races 0 and 1. Prior to thisdiscovery, resistance to P. infestans races 0 and 1 in plants designatedas LA 2533 had been unknown. Lycopersicon pimpinellifolium plantsdesignated as LA 2533 contain the allele(s) which confers resistance tothe tomato strain of P. infestans races 0 and 1. However, one skilled inthe art would recognize that any Lycopersicon pimpinellifolium whichcontains the allele(s) and is resistant to the tomato strain of P.infestans races 0 and 1 can be used in this invention.

The plants of the present invention can be prepared by traditionalbreeding techniques. For example, seed from Lycopersiconpimpinellifolium plants designated as LA 2533 can be used. Seeds of LA2533 are planted in a greenhouse or in a field. The resulting plants areexposed to the tomato strains of P. infestans, races 0 and 1. Aftersufficient disease pressure, those plants exhibiting the best resistanceare selected. Resistance to P. infestans races 0 and 1 may be determinedin two ways. The first way to determine resistance to P. infestansinvolves using what is called a "greenhouse screen". In a greenhousescreen, tomato seedlings are grown until the fifth true leaf starts toemerge. At this point, the plants are sprayed with a suspension of P.infestans race 1 sporangia, at a concentration of 10,000 sporangia permilliliter of solution. After inoculation, the plants are placed in achamber with 100% humidity for 24 hours. Next, they are removed from thehumidity chamber to a greenhouse bench in order to allow the disease todevelop. Resistant plants are identified and selected in approximately 7days. The plants can then be sprayed a second time with a suspension ofP. infestans race 0 in the same manner. However, many times it is notnecessary to test a plant for resistance to P. infestans race 0 becauseit is generally well known by those of ordinary skill in this art that atomato plant resistant to P. infestans race 1 is more likely than not tobe resistant to race 0 as well.

The second way of determining resistance to P. infestans races 0 and 1involves a field screen. A field screen involves transplanting seedlingsinto a field trial where the weather conditions favor natural infectionand disease development. Resistant plants are identified and selectedafter the disease has developed, approximately when the plants start toset fruit.

The inventors of the present invention devised a disease rating scalefor evaluating whether the plants produced by the method of thisinvention are resistant or susceptible to P. infestans, races 0 and 1.The disease rating scale is based on a numerical designation from 1 to 5that is more specifically described as follows: 1 corresponds to no orsmall lesions on the foliage only; 2 corresponds to no or small lesionson the foliage, expanding foliage lesions and small lesions (2 mmdiameter) on the petiole; 3 corresponds to no or small lesions on thefoliage, expanding foliage lesions and small lesions (2 mm diameter) onthe petiole, plus expanding lesions on the petiole; 4 corresponds to noor small lesions on the foliage, expanding foliage lesions and smalllesions (2 mm diameter) on the petiole, expanding lesions on thepetiole, plus small lesions (2 mm diameter) on the stem; and 5corresponds to no or small lesions on the foliage, expanding foliagelesions and small lesions (2 mm diameter) on the petiole, expandinglesions on the petiole, small lesions (2 mm diameter) on the stem, plusexpanding lesions on the stem or a dead plant. Plants with a diseaserating of less than three are considered resistant, while plants with adisease rating of three or greater are considered susceptible.

Traditionally, most plant breeders do not evaluate, identify and selectfor tomatoes that exhibit resistance to P. infestans. Most breeders donot work with P. infestans out of concern that the presence of thisfungus might wipe out their entire crop. Instead, most breeders sprayfungicides to control P. infestans in an effort to keep the fungus fromaffecting their crops.

The plants that exhibit the best resistance are then crossed withcommercial tomato plants (L. esculentum) by placing the pollen from oneplant on the stigma of the other. After the tomato fruit develops, seedis collected. The seeds are grown into plants and evaluated for diseaseresistance. Resistant plants are selected and may be backcrossed withcommercial tomato plants possessing desirable phenotypic traits such asplant type (determinate vs. indeterminate), fruit size, shape, flavor,color and long shelf life. The backcrossing may be continued until avariety is obtained that possesses desirable phenotypic traits and isresistant to the tomato strains of P. infestans races 0 and 1. Theresulting plants are stable to P. infestans race 1 in the field underhigh disease pressure.

It is interesting to note that Lycopersicon esculentum is cleistogamous.Therefore, it is very unlikely in the wild that cross pollinationbetween Lycopersicon pimpinellifolium and Lycopersicon esculentum wouldoccur without human technical intervention. It is also unlikely that theidentification, selection and backcrossing for the alleles(s) thatconfer resistance to P. infestans races 0 and 1 would occur naturally.

Protoplast fusion can also be used to create the plants of the presentinvention. For example, a first protoplast is obtained from aLycopersicon pimpinellifolium designated LA 2533 and a second protoplastis obtained from a Lycopersicon esculentum. The protoplasts are thenfused using traditional protoplast fusion procedures which are wellknown in the art.

For example, the protoplast fusion may be accomplished by employingpolyethylene glycol (PEG) causing agglutination, in the presence of afusion buffer, i.e., a high pH solution to let the membranes fuse. Suchsomatic hybridization may be effected under the conditions disclosed bySundberg et al. (Plant Science, 43, (1986) 155), hereby incorporated byreference, for the production of interspecific hybrids or modificationsthereof. However, one skilled in the art would recognize that theprotoplast fusion can be accomplished in other ways other than usingpolyethylene glycol (PEG). For example, the protoplasts can be fused byusing electric field-induced fusion techniques as described by Koop etal. (1989) "Electric Field-Induced Fusion and Cell Reconstruction-withPreselected Single Protoplasts and Subprotoplasts of Higher Plants" inElectroporation and Electrofusion in Cell Biology, Neuman et al.editors, pgs. 355-365, herewith incorporated by reference. Additionally,protoplast fusion can be accomplished with dextran and polyvinyl alcoholas described by Hauptmann et al., "Carrot x Tobacco Somatic Cell HybridsSelected by Amino Acid Analog Resistance Complementation", 6thInternational Protoplast Symposium, Basel, Aug. 12-16, 1983, herewithincorporated by reference.

By way of example and not limitation, examples of the present inventionwill now be given.

EXAMPLE 1

Several different plants were evaluated for possible P. infestansresistance. The following seeds were obtained: L. pimpinellifoliumdesignated LA 373, L. esculentum var. cerasiforme designated as LA 1338,L. pimpinellifolium designated LA 1375, L. hirsutum designated as LA2650,and L. pimpinellifolium designated as LA 2533 (Hope 84). All ofthese seedswere obtained from the Rick Center at the University ofCalifornia-Davis inDavis, Calif. Hope 33 is a tomato line that hastolerance to P. infestans race 0 and race 1. Celebrity and Fandango arecommercial varieties which do not exhibit any resistance to P.infestans.

The seeds were planted in a greenhouse. Tomato seeds were planted intosoil(50% peatmoss: 50% sand) and placed on a bench in the greenhouse(75° F. day and 70° F. night temperature) and watered as needed. Whenthe tomato seedlings had reached the fifth true leaf stage they wereinoculated with P. infestans race 1. The seedlings were sprayed with thesuspension of P. infestans sporangia at a concentration of10,000sporangia per milliliter of solution until run off. Afterinoculation, the plants were placed in a chamber with 100% humidity for24 hours. Next, theplants were uncovered and the disease allowed todevelop. Resistant plants were identified and selected approximately 7days after inoculation using the following disease ratings. These samelines mentioned above were also evaluated in the same manner with P.infestans race 0.

Disease Rating:

1=No or small lesions on the foliage only.

2=Above, plus expanding foliage lesions and small lesions (2 mmdiameter) on the petiole.

3=Above, plus expanding lesions on the petiole.

4=Above, plus small lesions (2 mm diameter) on the stem.

5=Above, plus expanding lesions on the stem or dead plant.

The results of the disease rating are provided in Table 1.

                  TABLE 1    ______________________________________                  DISEASE RATING    HOST            RACE 1   RACE 0   # OF PLANTS    ______________________________________    Hope 33         3.0      1.0      9    Celebrity       5.0      2.3      9    Fandango        5.0      2.3      9    LA 373 L. pimpinellifolium                    5.0      3.0      6    LA 1338 L. esculentum var.                    5.0      1.3      6    cerasiforme    LA 1375 L. pimpinellifolium                    4.3      1.0      6    LA 2650 L. hirsutum f. typicum                    4.3      1.2      6    LA 2533 L. pimpinellifolium                    1.3      1.0      6    ______________________________________

The above Table demonstrates that L. pimpinellifolium plants designatedas LA 2533 had a high level of resistance to P. infestans races 0 and 1whereas other L. pimpinellifolium lines desinated as LA 373 and 1375 didnot demonstrate a high level at resistance.

EXAMPLE 2

A L. pimpinellifolium plant designated LA 2533 and also referred to asHope84, was crossed with a tomato (L. esculentum) plant designated Fla7065. Plant Fla 7065 is determinate, large fruited, uniform green, freshmarket,firm inbred breeding line that has been released from Dr. JayScott's breeding program at the University of Florida, in Florida. Seedsresultingfrom this cross (F1) were planted into soil and grown in agreenhouse, and inoculated with P. infestans race 1 as previouslydescribed in Example 1. All the seedlings from this screen were rated asa 1 or 2 using the same disease rating described in Example 1,indicating that they were resistantto P. infestans, races 0 and 1. Thissuggests that the gene(s) responsible for resistance are inherited in adominant fashion.

EXAMPLE 3

The F1 plants described in Example 2 were self-pollinated. Seedlingsresulting from this (F2) were planted into soil and grown in agreenhouse.After several weeks, the seedlings were transplanted into afield, watered by drip irrigation and allowed to grow to maturity. Priorto flowering, cuttings were taken, transplanted into soil and grown in agreenhouse. Twoweeks after the cuttings were taken, they were inoculatedwith sporangia ofP. infestans, race 1 (concentration: 10,000sporangia/milliliter) and placed in a chamber at 100% humidity for 24hours. After twenty-four hours, the plants were removed and the diseaseallowed to develop. The cuttings were rated on a disease rating scale of1-5 after 14 days. The disease ratings used were as follows:

Disease rating:

1=No or small lesions on the foliage only.

2=Above, plus expanding foliage lesions and small lesions (2 mmdiameter) on the petiole.

3=Above, plus expanding lesions on the petiole.

4=Above, plus small lesions (2 mm diameter) on the stem.

5=Above, plus expanding lesions on the stem or dead plant.

The rating for the F2 plants are provided in Table 2.

                                      TABLE 2    __________________________________________________________________________    Line       #  Mean             Line                #  Mean                      Line                         #  Mean                               Line #  Mean    __________________________________________________________________________    94FH       120          1.0             94FH                 97                   1.3                      94FH                         123                            2.0                               94FH 146                                       3.0    94FH       126          1.0             94FH                109                   1.4                      94FH                         189                            2.0                               94FH 180                                       3.2    94FH        99          1.0             94FH                169                   1.4                      94FH                         107                            2.1                               94FH  93                                       3.5    94FH       148          1.0             94FH                158                   1.5                      94FH                         157                            2.2                               94FH 141                                       3.5    94FH       151          1.0             94FH                156                   1.5                      94FH                          94                            2.2                               94FH 125                                       3.7    94FH       186          1.0             94FH                187                   1.5                      94FH                         140                            2.2                               94FH 113                                       3.7    94FH       114          1.0             94FH                115                   1.5                      94FH                         101                            2.2                               94FH  90                                       3.8    94FH        98          1.0             94FH                104                   1.5                      94FH                         165                            2.3                               94FH 116                                       4.0    94FH       171          1.0             94FH                182                   1.5                      94FH                         159                            2.3                               94FH 188                                       4.0    94FH       162          1.0             94FH                177                   1.6                      94FH                         150                            2.5                               94FH 102                                       4.3    94FH       172          1.0             94FH                183                   1.6                      94FH                          92                            2.5                               94FH 155                                       4.3    94FH       170          1.0             94FH                166                   1.7                      94FH                         135                            2.5                               94FH 128                                       4.5    94FH       121          1.0             94FH                167                   1.7                      94FH                         149                            2.5                               94FH 178                                       4.7    94FH       127          1.0             94FH                124                   1.7                      94FH                         142                            2.5                               94FH  96                                       5.0    94FH       184          1.0             94FH                103                   1.7                      94FH                         174                            2.5                               94FH 129                                       5.0    94FH       100          1.2             94FH                176                   1.7                      94FH                         137                            2.7                               94FH  95                                       5.0    94FH       119          1.2             94FH                118                   1.7                      94FH                         153                            2.7                               94FH 110                                       5.0    94FH       154          1.2             94FH                106                   1.8                      94FH                         108                            2.7                               Celebrity                                    5.0    94FH       160          1.2             94FH                179                   1.8                      94FH                         143                            2.8                               Hope 33                                    3.2    94FH       181          1.2             94FH                168                   1.8                      94FH                         152                            3.0                               Hope 84                                    1.4    94FH       185          1.2             94FH                164                   1.8                      94FH                         117                            3.0    94FH       139          1.3             94FH                173                   1.8                      94FH                         144                            3.0    94FH       161          1.3             94FH                138                   2.0                      94FH                          91                            3.0    94FH       111          1.3             94FH                175                   2.0                      94FH                         105                            3.0    94FH       147          1.3             94FH                145                   2.0                      94FH                         122                            3.0    94FH       163          1.3             94FH                112                   2.0                      94FH                         136                            3.0    __________________________________________________________________________

Those lines with a disease rating of 2.9 or less were consideredresistant,while those lines with a disease rating of 3.0 or greater wereconsidered susceptible (71 lines resistant: 24 lines susceptible). Thedata in table 2 supports the 3:1 resistant to susceptible ratio, whichwould be expectedif the resistance loci was dominantly inherited.However, a number of lineshad a disease rating between 2.0-2.8. Theinventors believe that it is possible that these lines areheterozygotes. If this is true, then this would suggest that resistanceis partially dominant where the homozygous plants have a higher level ofresistance than heterozygous plants.

EXAMPLE 4

The F2 plants of Example 3 were self-pollinated. Seedlings resultingfrom this (F3) were planted into soil and grown in a greenhouse. Afterseveral weeks, the seedlings were transplanted into a field where theweather conditions favored natural infection and disease development ofP. infestans race 1. Severe disease pressure became apparent as thesusceptible control plants were dead (Celebrity). Plants were rated on ascale of 1-5 when the plants started to set fruit. The disease ratingsused were as follows:

1=No or small lesions on the foliage only.

2=Above, plus expanding foliage lesions and small lesions (2 mmdiameter) on the petiole.

3=Above, plus expanding lesions on the petiole.

4=Above, plus small lesions (2 mm diameter) on the stem.

5=Above, plus expanding lesions on the stem or dead plant.

The results are listed below in Table 3.

                                      TABLE 3    __________________________________________________________________________    Line #                                          Mean    __________________________________________________________________________    94AGH         103            1 1 1 1 1 1 1 1 1 1 1 1 1 1 1           1.0    94AGH         148            1 1 1 1 1 1 1 1 1 1 1 1 1 1 1           1.0    94AGH         162            1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1         1.0    94AGH         187            1 1 1 1 1 1 1 1 1 1 1 1 1               1.0    94AGH         158            1 1 1 1 1 1 1 1 1 1 1 1 1 1 2           1.1    94AGH         99 1 1 1 1 1 1 1 1 1 1 1 2                 1.1    94AGH         184            1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2       2                                                    1.1    94AGH         172            1 1 1 1 1 1 1 1 1 1 1 1 1 2 2           1.1    94AGH         98 1 1 1 1 1 1 1 1 1 1 1 1 2 2             1.1    94AGH         157            1 1 1 1 1 1 1 1 1 1 1 2 2               1.2    94AGH         100            1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2       2                                                    2                                                    1.2    94AGH         168            1 1 1 1 1 1 1 1 1 2 2                   1.2    94AGH         114            1 1 1 1 1 1 1 1 1 1 1 1 1 2 3           1.2    94AGH         183            1 1 1 1 1 1 1 1 1 1 1 1 2 2 2           1.2    94AGH         115            1 1 1 1 1 1 1 1 1 1 1 2 2 2             1.2    94AGH         186            1 1 1 1 1 1 1 1 1 1 1 1 1 3 3           1.3    94AGH         156            1 1 1 1 1 1 1 1 1 1 2 2 3               1.3    94AGH         112            1 1 1 1 1 1 1 1 1 2 2 3                 1.3    94AGH         119            1 1 1 1 1 1 1 1 1 1 2 2 2 3             1.4    94AGH         160            1 1 1 1 1 1 1 1 1 1 1 1 2 2 3 3         1.4    94AGH         133            1 1 1 1 2 2 2 2 2 1 1 1 1               1.4    94AGH         167            1 1 1 1 1 1 1 2 2 3                     1.4    94AGH         120            1 1 1 1 1 1 1 1 1 2 2 2 3 3             1.5    94AGH         159            1 1 1 1 1 1 1 2 2 2 3 3                 1.6    94AGH         170            1 1 1 1 1 1 1 1 2 3 3 3                 1.6    94AGH         121            1 1 1 1 1 1 1 2 2 2 2 3 3               1.6    94AGH         181            1 1 1 1 1 1 1 1 3 3 3 3 3               1.8    94AGH         109            1 1 1 1 1 2 2 2 2 2 2 3 3 3             1.9    94AGH         144            1 1 1 1 1 1 1 2 3 3 3 3 4               1.9    94AGH         138            1 1 1 1 1 1 1 2 3 3 3 3 3 3             1.9    94AGH         97 1 1 2 3 3                               2    94AGH         125            1 1 1 1 1 1 1 2 3 3 3 3 5               2    94AGH         166            1 1 1 1 2 2 2 2 3 3 3 3                 2    94AGH         174            1 1 1 1 1 1 1 3 3 3 4 4                 2    94AGH         108            1 1 1 1 1 1 2 2 2 2 3 3 3 3 3 4         2.1    94AGH         137            1 1 1 1 1 1 2 3 3 3 3 3 4               2.1    94AGH         132            1 1 1 1 1 1 1 1 2 3 3 3 3 3 3 3 3       4                                                    2.1    94AGH         161            1 1 1 1 1 2 2 2 2 2 3 3 3 3 3 4         2.1    94AGH         179            1 1 1 1 1 2 2 3 3 3 3 5                 2.2    94AGH         136            1 1 1 1 1 2 2 2 2 3 3 3 3 3 3 4         2.2    94AGH         171            1 1 1 1 1 1 2 2 3 3 3 3 3 3 3 4         2.2    94AGH         111            1 1 1 1 1 1 2 2 2 3 3 3 3 5 5           2.3    94AGH         135            1 1 1 1 2 3 3 3 3 3 3 3 3               2.3    94AGH         104            1 1 1 1 1 1 1 2 2 3 3 3 3 3 3 4 4       5                                                    2.3    94AGH         126            1 1 1 1 2 2 3 3 3 3 3 3 3 3 3           2.3    94AGH         151            2 2 2 2 2 2 2 2 3 3 3 3                 2.3    94AGH         154            1 1 2 2 2 2 2 2 3 3 3 3 3 3 3           2.3    94AGH         189            1 1 1 1 2 2 3 3 3 3 3 3 3 3 3           2.3    94AGH         143            1 1 1 2 2 2 2 2 3 3 3 3 3 5             2.4    94AGH         127            1 1 1 1 1 1 2 3 3 3 3 3 3 4 4 4         2.4    94AGH         185            1 1 1 1 1 2 2 2 3 3 3 3 3 3 4 4 4       2.4    94AGH         164            1 2 2 2 2 2 3 3 3 3 3 4                 2.5    94AGH         169            1 1 1 1 2 3 3 3 3 4 4 4                 2.5    94AGH         106            1 1 1 1 1 2 2 2 2 2 3 3 3 3 4 5 5       5                                                    2.6    94AGH         124            1 1 1 1 1 3 3 3 3 3 3 3 3 4 4 4         2.6    94AGH         173            1 1 1 3 3 3 3 3 3 3 3 3 3 3             2.6    94AGH         175            1 1 1 2 3 3 3 3 3 3 3 5                 2.6    94AGH         182            1 1 1 1 1 1 3 3 3 3 4 4 4 4 5           2.6    94AGH         176            1 1 1 1 1 1 1 3 3 5 5 5 5 5             2.7    94AGH         142            1 1 1 2 3 3 3 3 3 3 5 5                 2.8    94AGH         145            1 1 1 3 3 3 3 3 3 4 4 4                 2.8    94AGH         147            1 1 1 1 1 2 3 3 3 3 3 3 3 3 4 4 4       4                                                    4                                                    5                                                    2.8    94AGH         92 2 2 2 3 3 3 3 3 3 3 3 3 3 3 3 3         2.8    94AGH         105            2 2 2 2 2 3 3 3 3 3 3 3 3 3 4 4         2.8    94AGH         165            2 2 2 3 3 3 3 3 3 3 4                   2.8    94AGH         91 1 1 2 2 2 2 2 2 3 3 3 3 3 3 4 4 5       5                                                    5                                                    2.9    94AGH         122            1 2 2 2 3 3 3 3 3 5 5                   2.9    94AGH         117            2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 5       5                                                    5                                                    2.9    94AGH         102            3 3 3 3 3 3 3 3 3 3 3 3 3               3    94AGH         107            1 2 3 3 3 3 3 3 3 3 3 3 4 4 4           3    94AGH         101            1 1 2 2 2 2 2 2 3 4 5 5 5 5 5           3.1    94AGH         123            1 1 1 2 2 2 3 3 5 5 5 5 5               3.1    94AGH         153            2 2 2 3 3 3 3 3 3 3 4 4 4 5             3.1    94AGH         118            2 2 2 2 2 3 3 3 3 3 3 5 5 5 5           3.2    94AGH         140            2 3 3 3 3 3 3 4 4 4 4                   3.3    94AGH         96 3 3 3 3 3 4 4                           3.3    94AGH         94 3 3 3 3 3 3 3 4 4 4                     3.3    94AGH         150            3 3 3 3 3 3 3 3 3 3 4 4 4 5             3.4    94AGH         90 3 3 3 3 3 3 3 3 3 3 4 4 4 4 4 4         3.4    94AGH         134            1 1 1 2 3 3 3 4 4 4 4 4 5 5 5 5 5       3.5    94AGH         180            1 3 3 3 3 3 3 3 3 3 3 5 5 5 5 5         3.5    94AGH         149            2 3 3 3 3 3 3 3 3 3 4 4 4 4 5 5 5       5                                                    3.6    94AGH         146            3 3 3 3 4 4 4 4 4 4 4 4 5               3.8    94AGH         141            3 3 4 4 4 4 4 4 4 4 4 4 4 4 4 4         3.9    94AGH         113            3 3 3 3 3 4 4 5 5 5 5                   3.9    94AGH         188            3 3 4 4 4 4 4 4 4 4 4 4 5               3.9    94AGH         93 3 3 3 3 3 4 4 4 4 4 5 5 5 5             3.9    94AGH         130            4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4       4    94AGH         152            3 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 5       5                                                    4.1    94AGH         128            3 3 3 3 4 4 4 4 4 5 5 5 5 5             4.1    94AGH         129            3 3 3 3 3 4 4 4 4 4 4 5 5 5 5 5 5       5                                                    5                                                    4.2    94AGH         163            4 4 4 4 4 4 4 4 4 4 4 4 4 5 5 5         4.2    94AGH         177            4 4 4 4 4 4 4 4 4 4 4 5 5 5             4.2    94AGH         116            4 4 4 4 4 4 4 4 4 4 4 4 4 5 5 5 5       5                                                    4.3    94AGH         110            3 4 4 4 5 5 5 5                         4.4    94AGH         95 4 4 4 5 5                               4.4    94AGH         155            4 4 4 5 5 5 5 5 5 5 5 5 5 5 5 5 5       5                                                    4.8    94AGH         178            4 4 5 5 5 5 5 5 5 5 5 5 5 5 5 5         4.9    94AGH         131            5 5 5 5 5 5 5 5 5 5 5 5 5 5             5    Hope 84 1 1 1 1 1 1 1 1 1 1 1 1 1 2 2 2 2       1.2    Celebrity            5 5 5 5 5 5 5 5 5 5 5 5 5 5 5           5.0    __________________________________________________________________________

The above results confirm the results from the F2 plants described inExample 3. The homozygous resistant (94FH98, 94FH99, 94FH114, 94FH120,94FH121, 94FH148, 94FH162, 94FH170) and susceptible (94FH95, 94FH110,94FH116, 94FH128, 94FH129, 94FH155, 94FH178, 94FH188) plants identifiedinthe F2 plants gave the same disease rating in the F3 plants. Ifresistance was conferred by a number of genes (multigenic complex), thenit would notsegregate in the 3:1 ratio and the homozygous resistantplants would not beidentified as easily and as rapidly as demonstrated.

The invention described and claimed herein is not to be limited in scopebythe specific embodiments herein disclosed, since these embodiments areintended as illustrations of several aspects of the invention. Anyequivalent embodiments are intended to be within the scope of thisinvention. Indeed various modifications of the invention in addition tothose shown and described herein will become apparent to those skilledin the art from the foregoing description. Such modifications are alsointended to fall within the scope of the appended claims.

We claim:
 1. A method for producing tomato plants which are resistant tothe tomato strain of Phytophthora infestans races 0 and 1, the methodcomprising the steps of:a. providing a Lycopersicon pimpinellifoliumplant designated as LA 2533 having ATCC Accession Number 97382; b.crossing the Lycopersicon pimpinellifolium plant provided in step a witha Lycopersicon esculentum plant; c. collecting the seeds resulting fromthe cross in step b; d. regenerating the seeds into plants; e.inoculating the plants with the tomato strain of Phytophthora infestansraces 0 and 1; f. evaluating the plants of step e for resistance toPhytophthora infestans races 0 and 1; g. identifying plants which areresistant to Phytophthora infestans races 0 and 1; and h. selecting theplants that are resistant to Phytophthora infestans races 0 and
 1. 2.The method of claim 1 wherein the plants are evaluated using a diseaserating scale, wherein said disease rating scale comprises a numericalsystem from 1 to 5 where 1 corresponds to no or small lesions on thefoliage only; 2 corresponds to no or small lesions on the foliage, plusexpanding foliage lesions and small lesions (2 mm diameter) on thepetiole; 3 corresponds to no or small lesions on the foliage, expandingfoliage lesions and small lesions (2 mm diameter) on the petiole, plusexpanding lesions on the petiole; 4 corresponds to no or small lesionson the foliage, expanding foliage lesions and small lesions (2 mmdiameter) on the petiole, expanding lesions on the petiole, plus smalllesions (2 mm diameter) on the stem; and 5 corresponds to no or smalllesions on the foliage, expanding foliage lesions and small lesions (2mm diameter) on the petiole, expanding lesions on the petiole, smalllesions (2 mm diameter) on the stem, plus expanding lesions on the stemor a dead plant.
 3. The method of claim 1 wherein the plants areevaluated using a disease rating scale, wherein said disease ratingscale comprises a numerical system from 1 to 5 and 1 corresponds to noor small lesions on the foliage only; 2 corresponds to no or smalllesions on the foliage, plus expanding foliage lesions and small lesions(2 mm diameter) on the petiole; 3 corresponds to no or small lesions onthe foliage, expanding foliage lesions and small lesions (2 mm diameter)on the petiole, plus expanding lesions on the petiole; 4 corresponds tono or small lesions on the foliage, expanding foliage lesions and smalllesions (2 mm diameter) on the petiole, expanding lesions on thepetiole, plus small lesions (2 mm diameter) on the stem; and 5corresponds to no or small lesions on the foliage, expanding foliagelesions and small lesions (2 mm diameter) on the petiole, expandinglesions on the petiole, small lesions (2 mm diameter) on the stem, plusexpanding lesions on the stem or a dead plant.
 4. The method of claim 1further comprising the steps of backcrossing the plants in step h withLycopersicon esculentum plants having desirable phenotypic traits for asufficient number of generations to obtain Lycopersicon esculentumplants that are resistant to Phytophthora infestans races 0 and 1 andhave desirable phenotypic traits.
 5. The method of claim 1 furthercomprising the steps of self-crossing the plants of step h for asufficient number of generations to obtain plants that are fixed for anallele that confers resistance to the tomato strain of Phytophthorainfestans races 0 and 1 in the plants; and backcrossing the plants withLycopersicon esculentum plants having desirable phenotypic traits toobtain Lycopersicon esculentum plants that are resistant to Phytophthorainfestans races 0 and 1 and have desirable phenotypic traits.
 6. Themethod of claim 1 wherein the plants are evaluated using a diseaserating scale, wherein said disease rating scale comprises a numericalsystem from 1 to 5 where 1 corresponds to no or small lesions on thefoliage only; 2 corresponds to no or small lesions on the foliage, plusexpanding foliage lesions and small lesions (2 mm diameter) on thepetiole; 3 corresponds to no or small lesions on the foliage, expandingfoliage lesions and small lesions (2 mm diameter) on the petiole, plusexpanding lesions on the petiole; 4 corresponds to no or small lesionson the foliage, expanding foliage lesions and small lesions (2 mmdiameter) on the petiole, expanding lesions on the petiole, plus smalllesions (2 mm diameter) on the stem; and 5 corresponds to no or smalllesions on the foliage, expanding foliage lesions and small lesions (2mm diameter) on the petiole, expanding lesions on the petiole, smalllesions (2 mm diameter) on the stem, plus expanding lesions on the stemor a dead plant.
 7. A tomato plant which is resistant to the tomatostrain of Phytophthora infestans races 0 and 1 produced by the method ofclaim
 1. 8. Seed produced by the plant of claim
 7. 9. A tomato plantwhich contains an allele that confers resistance to the tomato strain ofPhytophthora infestans races 0 and 1 produced by the method of claim 1.10. Seed produced by the plant of claim
 9. 11. A method of producingseeds that result in tomato plants resistant to the tomato strain ofPhytophthora infestans races 0 and 1, the method comprising the stepsof:a. providing a Lycopersicon pimpinellifolium in plant designated asLA 2533 having ATCC Accession Number 97382; b. crossing the Lycopersiconpimpinellifolium plant provided in step a with a Lycopersicon esculentumplant; and c. collecting seeds resulting from the cross in step b, whichwhen planted, produce tomato plants which are resistant to the tomatostrain of Phytophthora infestans races 0 and
 1. 12. A method forproducing seeds that result in tomato plants resistant to the tomatostrain of Phytophthora infestans races 0 and 1, the method comprisingthe steps of:a. providing a Lycopersicon pimpinellifolium plantdesignated as LA 2533 having ATCC Accession Number 97382; b. crossingthe Lycopersicon pimpinellifolium plant provided in step a with aLycopersicon esculentum plant; c. collecting the seeds resulting fromthe cross in step b; d. regenerating said seeds into plants; e.inoculating the plants with the tomato strain of Phytophthora infestansraces 0 and 1; f. evaluating the plants of step e for resistance toPhytophthora infestans races 0 and 1; g. identifying plants which areresistant to Phytophthora infestans races 0 and 1; h. selecting theplants that are resistant to Phytophthora infestans races 0 and 1; i.backcrossing the plants in step h with Lycopersicon esculentum plantshaving desirable phenotypic traits for a sufficient number ofgenerations to obtain Lycopersicon esculentum plants that are resistantto Phytophthora infestans races 0 and 1 and have desirable phenotypictraits; and j. collecting the seeds produced from the plants of step iwhich when planted, produce tomato plants which are resistant to thetomato strain of Phytophthora infestans races 0 and
 1. 13. A method forproducing seeds that result in tomato plants resistant to the tomatostrain of Phytophthora infestans races 0 and 1, the method comprisingthe steps of:a. providing a Lycopersicon pimpinellifolium plantdesignated as LA 2533 having ATCC Accession Number 97382; b. crossingthe Lycopersicon pimpinellifolium plant provided in step a with aLycopersicon esculentum plant; c. collecting the seeds resulting fromthe cross in step b; d. regenerating the seeds into plants; e.inoculating the plants with the tomato strain of Phytophthora infestansraces 0 and 1; f. evaluating the plants of step e for resistance toPhytophthora infestans races 0 and 1; g. selecting the plants that areresistant to Phytophthora infestans races 0 and 1; h. self-crossing theplants in step g for a sufficient number of generations to obtain plantsthat are fixed for an allele that confers resistance to the tomatostrain of Phytophthora infestans races 0 and 1 in the plants; and i.backcrossing the plants produced in step h with Lycopersicon esculentumplants having desirable phenotypic traits to obtain Lycopersiconesculentum plants that are resistant to Phytophthora infestans races 0and 1 and have desirable phenotypic traits.